Apparatus for measuring and supervising the heart action



March 19, 1940. 5, STRAUSS r AL 2,193,945

APPARATUS FOR IEASURING AND SUPERVISING THE HEART ACTION Filed April 12,1937 2 Sheets-Sheet 1 March 19, 1940.

s. STRAUSS ET AL 2,193,945

APPARATUS FOR IEASURING AND SUPERVISING THE BEART ACTION Filed April 12,1937 2 Sheets-Sheet 2 Fig. 2

Patented Mar. 19, 1940 APPARATUS FOR MEASURING AND SUPER- VISING THEHEART ACTION Siegmund Strauss and Louis Weisglass, Vienna,

' Austria Application April 12, 1937, Serial No. 136,468 In AustriaApril 15, 1936 13 Claims. (Cl. lea-2.05)

The object of this invention is the provision of a device for constantlysupervising the bloodpressure and also, if desired, for simultaneouslymeasuring the frequency and the intensity of the pulse. A supervision ofthis kind is of great importance, especially in the case of surgicaloperations, in order to take immediately the necessary measures, whichin many cases may save the life 01' the patient, if the blood pressurefalls to a dangerously low value. It is usual to measure the bloodpressure. by means of a compression-bag or cufi applied to the upper armof the patient, inflated by a hand-pump and connected to a manometer. Ifthe pulse becomes imperceptible at the wrist of the arm being tested,this signifies that the pressure in the bag is equal or greater than thepressure of the blood in the compressed blood-vessels. In many cases, itis difficult to detect. the palpitation of the pulse with the finger andrequires, in the case of surgical operations, a specially trainedassistant who merely supervises the pulse. It has been proposed to pickup the pulse, for instance on the wrist, by means of a microphone and totransmit the impulses to a loud speaker over an amplifier. But in sucharrangements, difficulties are encountered because the microphone picksup disturbing noises which are also amplified and given out by the loudspeaker together with the so pulse beats. Acoustic feedback and howlingalso may easily occur and interfere. It has also been proposed toarrange a compression bag or cui! on the upper arm, said bag beingconnected to a manometer and to a motor-driven pump, and 35 to pick upthe pulse by means of a microphone arranged below in the bend of thearm, to amplify the impulses and to employ the amplified impulses incombination with a switch to switch the pump-motor on and ofiperiodically. If in 0 this known device (according to German patentspecification No. 512,430) when the pulse vanishes, the pressure in thecompression bag rises due to the fact that the pump continues to workuntil an alarm circuit is closed. This arrange- 45 ment, however, isvery complicated and has not only the disadvantages of all the devicesusing a microphone as a pick-up, but moreover the drawback that, ii thepulse ceases, the motor driven pump continues to work, so that thepressure in 50 the compression bag increases in a dangerous manner,unless further complicated safety devices are provided.

The object of the present inventionis to avoid these drawbacks.According to the invention, 55 two compression bags are provided, thefirst of which is, applied, for instance, on the upper arm, and receivesa measured pressure, while the second is applied to a blood vessel, forinstance to the artery on the wrist and receives the same pressure or aslightly higher or lower pressure. 5 The pulse in this blood vessel,which may be ---stopped by the inflation of the first bag, controlsvolume changes of said blood vessel and of the whole adjacent bodytissue and variations of the air pressure in the second bag. Thesevariations 10 are transmitted pneumatically to a manoazetric chamber inwhich they cause displacement of the manometric diaphragm. According tothe invention the movements of the diaphragm deform a piezo-electriccrystal and are thereby trans- 15 formed into electric pulsations, whichare employed to supervise the pulse beats and the heat action.

The drawings show by way of example an embodiment of the invention. Fig.1 shows scheg0 matically the two compression bags or cuffs and thepneumatic devices to connect the same to the measuring and indicatingdevices. This figure also shows in sectional perspective view the devicefor transforming the air pressure variations into electric impulses.Fig. 2 is a wiring diagram of the electric arrangement for measuring andsupervising the characteristic values of the pulse.

In Fig. 1, l0 and II are the two compression bags or cuffs which are ofwell known design. The first bag or cut! .10 is applied for instance tothe upper arm and is adapted to stop the circulation of the blood to anartery, for instance on the wrist, where the second cufl. H is applied.The compression cufis or bags may be, of course, also applied to otherparts of the body, the first bag 10 being always arranged nearer to thecenter of the blood circulation system and thesecond near to theperiphery of the same. The two bags 10 and H are connected for instanceby means of conduits I2, 13 with separate conduit systems. The conduitsl2, 13 may be ordinary thin flexible rubber tubes, which may besterilized and may have considerable length (up to 20 4.5 meters), sothat the device may be employed in the sick room or operation room in avery convenient and aseptic manner. The conduit system connected to thefirst cuff H1 is connected to a manometer l5 and preferably to an air tovessel 14. The latter has the purpose to compensate or smooth out smallvariations of pressure occurring if the tube 12 and especially theair-pressure bag 10 is accidentally compressed. The manometer 15indicates the blood pressure 2 arcane or its lower limit and has a largeam. Within the field of vision of said dial the dials of other measuringinstruments for the characteristic values of the pulse are arranged.'Ihis combination indicator is preferably arranged on a standard and sopositioned that the operating surgeon is able to observe it easily, inorder to be informed of the heart action condition of the patient at aglance.

The second compression bag or cui! II is connected by the conduit II andthe conduit system to a manometric chamber OI having a resilientdiaphragm l2. Either conduit system may be selectively connectedalternately by means of a three way cock II to a pump II, or

by way of three way cock 1 to the atmosphere, and the conduit systemconnected with cuff II is connected to the air vessel II.

In operation, after the three-way-cock 11 has been properly adjusted,the conduits II and II, cufi II and the manometric chamber 8| are putunder pressure by means of the hand-operated pump 18. The amount of thispressure is made preferably lower than the blood pressure and may beread on the manometer II. The pulse causes pressure variations in thebag II which are transmitted through tube 13 and conduit 80 to themanometric chamber II and cause mechanical vibrations of the diaphragml2 corresponding to the pulse beats. In order to transform thesemovements into electric impulses, a microphone of any known design andcircuit connection could be used, for instance a capacity microphone ora carbon compression contact. It has been found, however, that a piezoelectric crystal, for instance of Seignette salt, is especially adaptedfor this purpose. Said crystal is-deformed by the movement of thediaphragm and generates considerable electric voltages. 'Ihis crystal ishowever very easily breakable and delicate and is therefore arranged ina novel socket adapted to avoid any damage. This socket will bedescribed later in detail and also the manner in which the generatedelectric impulses are employed to directly indicate all the importantcharacteristic values of the pulse beats.

In order to measure the blood pressure, the bag III is inflated (thecooks being set accordingly) until the pulse vanishes, that is to say,no more electric impulses are to be observed. The blood pressure maythen be read upon the dial of the manometer ll. During the surgicaloperation the pressure in II is lowered to a certain value, say 10 mm.less, so that the impulses occur again. If the blood pressure dropsbelow this value, the impulses will cease again and after a certainlapse of time an alarm signal is given in a manner described later indetail. Simultaneously with this alarm signal an air escape valve I3 maybe opened. This valve is connected by a conduit with the tube 12 andtherefore causes a slow pressure drop in cufi ll until the impulsesoccur again.

The crystal l is carried by a socket or clamp 86, which is supported ina piece 88. This piece is pivotally supported by pivots 84 on twoextensions of the manometer casing ll. According to the invention, thepivoting movement may be effected only against a certain frictionalresistance caused by a spring 81 which is adJustable by means of a screw88 and acts, so to say, as support of the crystal I, said crystal beingacted upon on its point by the rod '3 attached to the diaphragm. Thecrystal is held against aid rod by means of a spring OI, the tension ofsaid spring being Just capable of overcoming the frictional resistance.In order to adjust said spring, a regulating device ll of any design isprovided. If the blood pressure drops heavily making necessary apressure drop in the bag II, the connecting rod 83 of the diaphragm isdisplaced. Due to the design according to the invention just described,the crystal follows the rod 03 under the influence of the spring 90 andconstantly remains in contact with the rod 83. Therefore, displacementsof the rod 83 with respect to the crystal have no influence because saidcrystal cannot lose contact with the rod. The screw '2 with the milledhead 93 makes it possible, to separate, the crystal from the rod 83 whendesired, for instance, for transporting the apparatus. It is, however,not possible to press the crystal against the rod 83 by hand. This canonly be done by the spring 80. In this manner it is made impossible tobreak the crystal, even by careless manipulation.

As shown in Fig. 2, a very high leak resistance 2 of about 20 megohms isconnected in parallel to the electrodes touching the crystal l. One

side of the crystal and the leak resistance is connected to apotentiometer 3 bridging a biasing battery 4 (of about 4 volts) which isconnected to the cathode of the first tube 6 and which may bedisconnected by means of the switch 5 if the device is not in use. Theother side of this parallel group (crystal and leak) is connected bymeans of a shielded conductor to the grid of tube 6. This tube ispreferably a, so-called, high frequency pentode which as far as possibleis free from residual gas, and has an indirectly heated cathode, thegrid being well insulated, and is led to the outside at the apex of theglass bulb. In the plate circuit oi this tube are arrangedshort-circuited terminals 1 for the connection of a measuringinstrument, and the operating resistance 8. The voltage across thisresistance is fed through a stabilizing resistance 9 in directconnection with the grid of the second tube ll. This tube It is adirectly heated power pentode, such as is commonly emplayed to actuate aloud speaker. The cathode of this tube, that is to say the center-tap ofits heating coil, is connected over a variable resistnegative grid biasfor the tube III is obtained.

This tube works as an anode bend rectifier and amplifier. The potentialsare kept constant by a voltage divider of low ohmic value or in a moreefilcient and reliable manner by a glowdischarge-voltage-divider II.This voltage divider is fed by a transformer 35 over a fullwaverectifier l6 and filtering devices (condenser-s 33, 32 and filterresistance 34). The plate circuit of tube It includes a limitingresistance, the relay coil ll shunted by a condenser Ii, and amilliammeter with the terminals It. The voltage drop across I! and thisinstrument is employed for the operation of a glow lamp with terminalsll. Fig. 1 shows the arrangement of this instrument and of the glow lampwith its connections. These connections are connected with the terminalsin Fig. 2 designated by the same reference numbers.

In operation, each pulse stroke generates an electric impulse in thecrystal I. This impulse This point is positive with means 3 is amplifiedand rectified by the directly coupled amplifier 2, l0, even if it hasvery low frequency and very fiat characteristic as for instance in thecase of old or sick persons. Each pulse stroke causes a flash of thelamp across II, a deflection of the pointer of the instrument betweenthe terminals I4, and an attraction of the armature of the relay II.

The glow lamp l5 serves to clearly indicate the pulse strokes andfurther offers the advantage that the voltage drop across the relay i1and the instrument between the terminals I4 is always kept constant at avalue of about volts (i, e. theglow-voltage of the .glow lamp).Therefore theoperatlon of the relay and the deflection of the instrumentalways takes place under optimal conditions. The glow lamp II is furtheradvantageous because its use makes possible the connection of aninstrument of relatively; high sensitivity to the terminals, thisinstrument being protected by the glow lamp which acts as a shunt ofrelatively low ohmic resistance as the glow discharge starts. Thesensitive instrument, however, makes possible an easy and comfortableadjustment of the amplifier by adjusting the grid bias of the tubes. Theplate current of the pentode ill is limited to a desired value by meansof the resistance ii.

In order to directly indicate the frequency of the pulse, each operationof the relay, as described in our Patent No. 2,114,578, dated April 19,1938, connects a small condenser is in parallel to a great condenser it,said great condenser being connected constantly through a highresistance 20 to a potential, which may be exactly regulated by means ofthe potentiometer 30. Thus, a certain amount of electricity is withdrawneach time from the condenser is, which is absorbed by short-circuitingthe condenser as the relay I1 is restored. Therefore, the potentialacross the condenser i! is a function of the number of pulsations pertime unit. In order to measure this potential, the same is transmittedover a further relay-contact and a resistance 2| (serving to filter outthe pulsations). to a condenser 22, this condenser being arrangedbetween the grid and the centertap of a filament-potentiometer 24 of atube 23 acting as a vacuum tube voltmeter. In the plate circuit of thistube, a milliammeter with terminals 25 is arranged, which is calibrateddirectly in pulse strokes per minute (Fig. 1).

In order to constantly supervise the intensity of the pulse-strokes, theamplifier has a double output circuit. For this purpose, it would bepossible to employ two tubes having their grids in parallel, the platecircuit of one of said tubes operating the relay, whilst the platecircuit of the other tube actuates a device for measuring theamplitudes. It is preferable to connect, as

shown in Fig. 2, the screen grid of the pentode ranged across theterminals 44 in the plate circult of the voltmeter tube 42. It ispossible, by 7 means of the variable resistance 21, to vary theamplification of the tube l0 and thereby to set the pointer oi theintensity meter to a predetermined position. In this manner, anyabnormal intensity of the heart-strokes is instantaneously made visible.The resistance 42 furnishes grid bias to the tube 42.

In order to give a signal after a' certain time delay, if the pulsestops because of a lowering of the blood pressure, two more contacts arearranged on relay At each operation of the relay said contacts connect acondenser 21. shunt ed by a resistance 20, to a charging potential. Thiscombination 2. 21 is arranged between grid and cathode of another tube28 and blocks this tube, as long as impulses are occurring, by chargingits grid with a negative potential. If the impulses cease the potentialfiows off and after a certain time, according to the time-constant of22, 21, the tube becomes conductive. A relay 22 in the plate circuit oftube 22 then closes the circuit of a buzzer 40 which may be disconnectedby means of a switch 48. In order to give a warning signal, if thisbuzzer 0 is disconnected, a pilot lamp is switched on at the same time.The pilot lamp 4 lights constantly and indicates the operating conditionof the device.

In order to compensate the influence of variations in the voltage of themains to the measure-- ments, the heaters of those tubes, which may beeflected by variations of the electron emission (such as especially thefirst stage tube I and the voltmeter tube 22), are connected to themains over a regulating tube 45 comprising iron filaments in anatmosphere of hydrogen; II is the main switch (combined with thevariable resistance voltage 21), I2 is a safety fuse and 5| aresistance, which if in connection with'220 volt serves asseriesresistance for the heating circuit of the tubes 0 and 22.

The device may be, of course, also operated by batteries or convertersinstead of the alternating current mains, and the alterations necessaryin this case are evident to any expert skilled in the art.

What we claim is:

1. A device for measuring and supervising the heart action comprisingtwo compression bags. one of said bags receivingla measured pressure andbeing applied to the body in such a manner that it is adapted tointercept the blood circulation towards an artery to which artery thesecond bag is applied, the second bag being acted upon by the volumealterations of the artery due to the blood circulation and beingpneumatically connected to a manometer having a chamber provided with adiaphragm. a piezoelectric crystal adapted to be deformed by themovement of said diaphragm and to generate electric impulses, adirect-coupled multi-stage amplifier amplifying and rectifying saidimpulses, a relay in the output circuit ofsaid amplifier, said relaybeing adaptedto shunt at each movement of its armature, a smallcondenser to a condenser connected for charging to a source of electricpotential over a resistance, means to indicate the potential across saidcharged condenser to thereby measure the frequency of the pulse, and arectifier connected to the output circuit of said amplifier adapted tomeasure the peak values of the amplified impulses for indicating theintensity of the pulse strokes.

2.- In a device according to claim 1, a glow lamp arranged in shunt tothe relay coil and to an indicating instrument in the output circuit ofthe amplifier.

3. A device according to claim 1, in which the last stage of theamplifier comprises a double output circuit, one output circuitoperating a relay, and the other output circuit the intensity measuringrectifier.

4. A device according to claim 1, in which the last stage of theamplifier comprises a pentode, the relay being arranged in the platecircuit of said pentode, the screen grid circuit of said pentodecontaining a resistance, the grid of a voltmeter-tube being connected tosaid resistance over said rectifier.

5. In a device according to claim 1, a variable resistance in thecathode circuit for regulating the amplification factor of the amplifierin or-' der to set the intensity measuring rectifier to a predeterminedindication.

6. A device according to claim 1. in which the heaters of the first tubeof the amplifier and the voltmeter-tube are arranged in series with aregulating tube.

7. In a device according to claim 1, additional contacts operated bysaid relay, said contacts operating an alarm device over a time delaydevice if the pulse strokes cease for too extended a period of time.

8. In a device according to claim 1, additional contacts operated bysaid relay, a condenser shunted by a resistance arranged between gridand cathode of a tube, said condenser receiving, by means of saidadditional contacts, a charge negative with respect to the grid at eachimpulse, and means in the plate circuit of said tube to operate an alarmdevice.

9. In a device according to claim 1, additional contacts operated bysaid relay, a condenser shunted by a resistance arranged between gridand cathode of a tube. said condenser receiving, by means of saidadditional contacts, a charge negative with respect to the grid at eachimpulse, and means in the plate circuit of said tube to operate an alarmdevice and to operate a valve relieving the air pressure in the firstcompression has 11. Apparatus according to claim 1, and means forfrictionally holding said piezo-electric crystal, and means forresiliently pressing said holding means so that the crystal isresiliently pressed against said motion transmitting connection, a handoperable means for lifting the crystal from the motion transmittingconnection, said means comprising a one way motion transmissionmechanism whereby said means is prevented from applying pressure on saidcrystal against said motion transmitting connection.

12. Apparatus according to claim 1. a movable socket holding thepiezo-electric crystal, a spring pressed against said socket andfrictionally holding said socket in position, a screw for applyingpressure adjustably on said spring to adjust the tension of said springagainst said socket and another spring for resiliently pressing saidcrystal against the motion transmitting connection to the manometerdiaphragm.

13. Apparatus according to claim 1, and a manometer for measuring andindicating the pressure of the first compression bag and having a largeindicating dial, the means for indicating the frequency and intensity ofthe electrical variations of the crystal responsive to the pulsecomprising smaller dials arranged within the area of said large dial.

SIEGMUND STRAUSS. LOUIS WEISGLASS.

